Age-related variation in threat-sensitive behavior exhibited by spotted hyenas: observational and experimental approaches

We examined ontogenetic variation in threat-sensitive behaviors exhibited by spotted hyenas (Crocuta crocuta). We documented naturally-occurring vigilance throughout ontogeny, and used playback experiments to evaluate age-related variation in hyenas' responses to control sounds or lion roars. We inquired whether juveniles respond to lions more cautiously than do adults. Naturalistic observations showed that juveniles are less vigilant than adults when no immediate threat is present, but more vigilant than adults when lions are present. Our playback experiments revealed that both adult and juvenile hyenas moved in response to lion roars but not to control sounds, and their reactions were stronger to roars emitted by male than female lions. However, juveniles showed a stronger response to lions than adults, as expressed by spending more time avoiding speakers after roar onset, and by having a shorter latency to first movement than adults. Like adults, juvenile hyenas, thus, appear to recognize certain signals as dangerous and respond accordingly. However, our data suggest that young hyenas may need experience with danger early in life to learn the environmental circumstances under which they ought to be vigilant when no threat is immediately apparent.